1. Field
Generally, the present invention relates to a heat exchanger of an air conditioner, and more particularly to a heat exchanger of a cooling and heating air conditioner.
2. Description of the Prior Art
Typically, a heat pump is composed of a compressor, an evaporator, a condenser, an expansion device, and in case of heating, a cycle is repeated where refrigerant is compressed to a high temperature, high pressurized refrigerant by a compressor, which is evaporated, and discharged to a condenser from which a high temperature heat is discharged to outside where temperature is lower. Alternatively, in case of cooling operation mode, a condenser operates as an evaporator and an evaporator functions as a condenser to allow the condensed refrigerant to heat-exchange with the hot outside air.
Referring to FIG. 1, a cooling cycle includes a compressor (COMP) for compressing a low temperature/pressure vaporized refrigerant to a high temperature/pressure vaporized refrigerant, a condenser (COND) for changing the high temperature/pressure vaporized refrigerant changed by the compressor (COMP) to a high temperature/pressure liquefied refrigerant and discharging heat to the outside, an expansion device (EXP) for changing the high temperature/pressure liquefied refrigerant changed by the condenser to a low temperature/pressure two phase refrigerant, and an evaporator (EVA) for changing the low temperature/pressure two phase refrigerant changed by the expansion device (EXP) to vaporized refrigerant and absorbing the outside heat.
In the cooling cycle thus described, a heat pump is configured in such a manner that heating and cooling can be selectively chosen by forwardly or reversely circulating the cooling cycle where heat is absorbed by the evaporator (EVA), and the heat is discharged by the condenser (COND).
Referring to FIG. 2, a heat pump includes a compressor (COMP) for compressing the refrigerant, an outdoor heat exchanger (Hout) connected to the compressor (COMP) via a pipe (P) for functioning as a condenser during cooling mode operation and functioning as an evaporator during heating operation mode, an indoor heat exchanger (Hin) connected to the compressor (COMP) via a pipe (P) for performing a vaporizing process during cooling operation mode and performing a condensing process during heating operation mode, a four-way valve (V) for supplying a high temperature/pressure refrigerant discharged from the compressor (COMP) to the outdoor heat exchanger (Hout) during cooling operation mode and to the indoor heat exchanger (Hin) during heating operation mode, and an expansion device (EXP) mounted at an outdoor side for expanding the condensed refrigerant.
In the heat pump thus configured, the four-way valve (V) sends the high temperature/pressure refrigerant discharged from the compressor (COMP) to the indoor heat exchanger (Hin) or to the outdoor heat exchanger (Hout) to cool or heat the air within a defined space according to the selection of cooling or heating operation mode.
In other words, the four-way valve (V) sends the high temperature/pressure refrigerant discharged from the compressor (COMP) to the outdoor heat exchanger (Hout) side during cooling operation mode, and to the indoor heat exchanger (Hin) side during heating operation mode. The outdoor heat exchanger (Hout) functions as a condenser to cool the high temperature/pressure refrigerant to a condensed liquefied state during cooling operation mode, and the condensed liquefied refrigerant passes an expansion valve (V) and is partially vaporized to move to the indoor heat exchanger (Hin) in a mixed state of gas and liquid.
The refrigerant is vaporized during cooling in the indoor heat exchanger (Hin) to function as an evaporator for cooling the air within a defined space, and the vaporized refrigerant passes the four-way valve (V) to re-enter the compressor (COMP) . Alternatively, in the heating operation mode, the outdoor heat exchanger (Hout) and the indoor heat exchanger (Hin) function in the reverse way such that an evaporating process is carried out in the outdoor heat exchanger (Hout) while the condensing process is conducted in the indoor heat exchanger (Hin).
Referring to FIG. 3, an indoor heat exchanger (Hin) according to the prior art includes a first heat exchange unit (10), a second heat exchange unit (20), a connecting pipe (P1) connecting the first heat exchange unit (10) to the second heat exchange unit (20), and an expansion valve (EXV) disposed at the connecting pipe (P1) for allowing both the first heat exchanger unit (10) and the second heat exchanger unit (20) to perform an evaporating function or a condensing function during cooling and heating operation modes and for allowing the first heat exchanger unit (10) to perform a condensing -function and the second heat exchanger unit (20) to perform an evaporating function during indoor fixed temperature humidity operation.
The first and second heat exchanger units (10.20) all function as an evaporator during cooling operation mode, and the refrigerant discharged from the compressor (COMP) is introduced into the first heat exchanger unit (10) via the outdoor heat exchanger (Hout) and the expansion device (EXP), and the refrigerant introduced into the first heat exchanger unit (10) passes through the opened expansion valve (EXV) to flow into the second heat exchanger unit (20) and to be sucked into the compressor (COMP) along an external pipe (P2) at the second heat exchanger unit (20) side.
During the heating operation mode, the first and second heat exchanger units (10.20) all function as a condenser, and the refrigerant discharged from the compressor (COMP) flows into the second heat exchanger unit (20), and the refrigerant introduced into the second heat exchanger unit (20) passes the opened expansion valve (EXV) to flow into the first heat exchanger unit (10) and again passes the expansion device (EXP) and the outdoor heat exchanger (Hout) along the external pipe (P2) at the first heat exchanger unit (10) to be sucked into the compressor (COMP)
Referring to FIG. 4, the number and position of a refrigerant inlet (11) and a refrigerant outlet (12) at the indoor heat exchanger (Hin) according to the prior art are arbitrarily constructed by a designer to obtain a maximum performance.
The refrigerant is greatly influenced by temperature and pressure depending on the property of gas, and amount of refrigerant varies depending on whether it is a cooling operation or a heating operation mode. As illustrated in FIG. 5, there is a problem in that a check valve (30) should be additionally mounted because a main cooling expansion device (EXP1) and an auxiliary heating expansion device (EXP2), each being different in size, should be respectively equipped for cooling and heating operation modes, wherein the main expansion device (EXP1) is operated during cooling and heating operation modes while the auxiliary expansion device (EXP2) is operated only during heating operation mode.